In conventional CMOS devices, such as inverters and logic gates, both p-channel and n-channel devices go through a linear region when both devices are "on" during the switching transient. The drain current which passes through both devices from power supply to ground is wasted ("pass-through" current). The pass-through current can be accurately determined by transient analysis simulation of such circuits without load, while monitoring the power supply current. The typical pass-through current of an inverter is shown at 6 in FIG. 1, which is a plot of pass-through current vs. time.
This problem is further compounded in a design of circuits operating at slower clock speeds of hundreds of kHz manufactured in short channel CMOS technology. This technology is capable of operating with clock speeds in the hundreds of MHz range, with gate delays of less than one nanosecond. The slower clock speeds cause an increase in the amount of time that the p-channel and n-channel devices are both "on", i.e. being "on" longer results in a greater time for current to flow from the power supply voltage to ground.
This problem is well illustrated in an oscillator circuit which is battery powered, and where the power consumption is one of the most critical parameters. Such application for a battery powered oscillator may be found in a pen-based computer, where the pen transmits signals which are used for position reconciliation between the pen and a pad or template. The frequency of the oscillator used in the pen is defined by external components. The signal waveform is sinusoidal.
It is an object of the present invention to provide an improved inverter circuit.
It is yet another object of the present invention to provide an improved CMOS inverter circuit.
It is yet another object of the present invention to provide an inverter circuit having reduced power consumption.
It is a further object of the present invention to provide an improved inverter circuit for use in an oscillator.
It is still another object of the present invention to provide circuits for reducing power dissipation in a electrical/electronic stylus such as a pen in a pen-based computer.